The present invention relates generally to an exposure apparatus, and, more particularly, a processing system for transporting an object, such as a mask, a semiconductor chip or a liquid crystal display substrate, etc., from a supplying part to a processing chamber for executing an exposure process in a fabricating process of the semiconductor chip or the liquid crystal display substrate, etc.
In manufacturing such fine semiconductor devices as a semiconductor memory and a logic circuit in photolithography technology, a reduction projection exposure apparatus for transferring a circuit pattern by a projection optical system projecting the circuit pattern onto a wafer, etc., has been conventionally used.
The critical dimension transferable by the projection exposure apparatus or the resolution is proportionate to a wavelength of light used for exposure, and inversely proportionate to the numerical aperture (“NA”) of the projection optical system. The shorter the wavelength is, the better the resolution becomes. Therefore, the exposure light uses a shorter wavelength with the demand for the fine processing to semiconductor devices in recent years, and use of the wavelength of the ultraviolet light has shifted from an ultra-high pressure mercury lamp (i-line (a wavelength of about 365 nm)) to a KrF excimer laser (a wavelength of about 248 nm) and an ArF excimer laser (a wavelength of about 193 nm).
The semiconductor device becomes minute so rapidly that the lithography using the ultraviolet light has a limit. Then, a reduction projection exposure apparatus (hereafter, it is called, an “EUV exposure apparatus”) using extreme ultraviolet light is developed to efficiently transfer a finer circuit pattern of 0.1 μm or less.
A chamber stores an exposure part of the exposure apparatus, and has a vacuum atmosphere to prevent attenuation of the exposure light, because the exposure light with such a short wavelength as the EUV light remarkably decreases at an ambient pressure.
Such a processing system arranges a load lock chamber to transfer a substrate as an object to be exposed between a chamber that houses in the exposure part and a substrate supplying part located under the ambient pressure (for instance, see Japanese Laid-Open Patent Application, Publication No. 10-092724). Here, the substrate as the object to be exposed is a mask (reticle) that has a circuit pattern and serves as an original edition, and means a transmitting type mask for transmitting the exposure light and a reflecting type mask for reflecting the exposure light.
FIGS. 18A and 18B are schematic block diagrams showing a configuration of a conventional processing system 1000. FIG. 18A is a sectional view, and FIG. 18B is a top view. The processing system 1000 has a high vacuum atmosphere in a processing chamber 1100 storing the exposure part. The processing chamber 1100 is connected with a reserving room 1110 storing a second transporter 1112.
A carrier mounting part 1310 as the substrate supply part is arranged in the ambient atmosphere, and a first transporter 1320 is arranged to access the carrier mounting part 1310 and the load lock chamber 1200. A clean booth 1300 is arranged to surround the first transporter 1320.
The load lock chamber 1200 includes a first gate valve 1220 for shielding between the load lock chamber 1200 and the carrier mounting part 1310 in the ambient atmosphere, and a second gate valve 1220 for shielding between the load lock chamber 1200 and the reserving room 1110.
A description will now be given of an operation of the processing system 1000. The first transporter 1320 takes out one mask from the carrier mounting on the carrier mounting part 1310, and transports the mask to the load lock chamber 1200. The first gate valve 1210 closes to shield the ambient atmosphere, and the load lock chamber 1200 exchanges the atmosphere after the mask is transported to the load lock chamber 1200 and is put on a mounting stage.
A description will now be given of a replacement of an atmosphere in the load lock chamber 1200. The vacuum-exhausting valve (not shown) opens when the clean booth 1300 and the processing chamber 1100 are shielded by closing the first gate valve 1210 and the second gate valve 1220, and then a vacuum pump (not shown) starts exhausting the gas of the load lock chamber 1200 through a vacuum-exhausting tube. The vacuum exhaustion is stopped by closing the vacuum-exhausting valve after the load lock chamber 1200 is exhausted to a predetermined degree of vacuum.
The second gate valve 1220 opens, and then the second transporter 1112 takes out the mask in the processing chamber 1100, and transports the mask to the exposure part stored in the processing chamber 1100 after the atmosphere replacement finishes in the load lock chamber 1200. The first transporter 1320 and the second transporter 1112 transport the mask for use with the exposure part to the carrier mounting part 1310 through the load lock chamber 1200 (for example, see Japanese Patent Application Publication Nos. 10-092724, 10-233423, 2000-123111, and 2001-085290).
However, when the mask is transported and the load lock chamber is replaced with the vacuum atmosphere, particles (contaminants) adhere to the mask disadvantageously. For instance, the particles swirl and adhere to the mask during the exhaust to replace the atmosphere of the load lock chamber. The particles adhered mask disadvantageously deteriorate the exposure, because a particle adhered part neither transmits nor reflects the exposure light (production of the exposure defect).
Thus, various methods are proposed to prevent the particles from adhering to the mask. For instance, it is proposed that a method arranges a pellicle to protect surfaces of particles with a transcript pattern, but this method may not apply because of a restriction of the material and the structure in the processing system using the EUV light, etc., with shorter wavelengths. It is difficult to use the material with the ultraviolet light or the visible radiation, because the material highly absorbs the light when the exposure light has a short wavelength. Thus, the material usable for a wavelength range of the EUV light does not exist.
Moreover, a method is proposed which arranges a detecting mechanism for detecting particles from adhering to the mask, in the processing chamber. However, this method decreases the throughput, because this processing chamber needs many components, a large size, and a long time to create a high vacuum atmosphere, since the detecting mechanism is arranged in the processing chamber maintained in a high vacuum atmosphere. Moreover, maintaining the high vacuum atmosphere becomes difficult. Although it is conceivable to arrange a detecting mechanism in the ambient environment (that is, a clean booth) for detecting the particles adhered to the mask, and to carry the mask into the processing chamber after the detecting mechanism detects the particles, this method cannot eliminate particles adhered during transportation.
On the other hand, another proposed method prevents swirls of the particles that adhere during a replacement to the vacuum atmosphere (that is, the exhaust is slowed down), and by exhausting slowly when the exhaust begins. However, the slow exhaust needs a long time from the ambient attainment to the high vacuum atmosphere, and the throughput decreases.